//如果浏览器支持canvas ,则不显示canvas中的p标签,反之,则显示
<!--<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
</head>
<body>
<canvas style="width:200; height: 400; background-color: red;">
<p>this not does not support the <code>canvas</code></p>
</canvas>
</body>
</html>-->